Cargo Features

[dependencies]
to-socket-addrs = { version = "0.2.1", default-features = false, features = ["sync", "async", "tokio", "test_dns_ipv6"] }
default = sync

The sync feature is set by default whenever to-socket-addrs is added without default-features = false somewhere in the dependency tree.

sync default
async

Enables async-std

tokio

Enables tokio

test_dns_ipv6

ToSocketAddrs has 5 features without comments.